JPH0472849B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to epoxy compositions. Epoxy resins can be converted into insoluble, difficult-to-process, crosslinked polymers by means of suitable curing agents. The above resin and curing agent are
It is also possible to construct one-component systems in which two components are stored in a ready-to-use mixture;
It is also possible to construct a two-component system in which the two components are stored separately until just before use. One-component systems are usually cheaper and easier to use than two-component systems, and they also require
It is very advantageous in that there is also no need for difficult processing in two-component systems where the components have to be mixed in precise proportions and amounts. The present invention relates to one-component systems. The curing agent used in one-component systems must be relatively unreactive with the epoxy resin at room temperature to keep the mixture of resin and curing agent stable until the temperature is raised to cure. The curing agent is required to not cause premature curing of the resin even when the one-component system is stored for a long time. Thus, it is highly desirable for the system to have a long shelf life. Imidazoles are known curing agents for epoxy resins, but cannot be used in one-component systems because of their high reactivity towards epoxides.
One approach to this problem is to complex the imidazole with a metal salt to produce a hardener that can be used with the epoxy in a one-component system that can be stored without premature curing. Such imidazole/metal salt complexes are described in GB 1204843. However, the complex has the disadvantage that it is a crystalline material with very low solubility in epoxy resins.
The solubility of curing agents in epoxy resins is highly desirable when used in one-component systems. With crystalline hardeners such as those described in GB 1024834, when the hardener is mixed with a resin,
A heterogeneous dispersion will be obtained. The dispersions tend to precipitate or agglomerate when stored for long periods of time. Furthermore, the dispersions are not ideal for the production of pre-impregnated composite materials (pre-pregs). The present invention first relates to (a) a metal salt complex of an adduct of an imidazole and a monofunctional epoxy compound;
(b) A one-component epoxy composition comprising an epoxy resin, a monoepoxide, or a mixture of an epoxy resin and a monoepoxide, which can be cured or polymerized by heating. Imidazole/epoxy adducts can be formed from essentially any imidazole or mixture of imidazoles. As used herein, "imidazole" means imidazole itself or any substituted imidazole. In this specification, "monofunctionality" means

[Formula] means one containing one group. Examples of substituted imidazoles that can be used are as follows. Alkylimidazoles such as 1-methylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-ethylimidazole and 2-ethyl-4-methylimidazole, carbamyl alkyl substituted imidazoles such as 1-(2-
Carbamethyl)imidazole and 1-(2-carbamylethyl)-2-ethyl-4-methylimidazole: alkaryl-substituted imidazoles such as 1-benzyl-2-methylimidazole and 1
-Phenyl-2-methylimidazole: alkenyl-substituted imidazole e.g. 1-vinyl-2-methylimidazole: allyl-substituted imidazole e.g. 1-allyl-2-ethyl-4-methylimidazole: carboxanilide-substituted imidazole e.g. 1
- Imidazolecarboxanilide and 2-methyl-1-imidazolecarboxanilide: benzimidazole, naphthimidazole: polymidazole: carbohydroxyethylamine: o-phenylenediamine and others such as 1-p-toluene. Mixed imidazoles, such as mixtures of imidazole and 1-methylimidazole and others, are used to form imidazole/epoxy adducts, which are complexed with metal salts to form the curing agent used in the compositions. You can also do that. Preferred imidazoles are imidazole and 2-ethyl-4(5)-methylimidazole. Preferably, the monofunctional epoxy compound used to form the imidazole epoxy adduct is an epoxy having up to 20 carbon atoms. Preferably,
The epoxy compound is a glycidyl ether, such as phenyl glycidyl ether. The adduct in the complex used in the composition can be formed in a molar ratio of imidazole:epoxy of 1:1 or 1:2, e.g.

[expression] or

[Formula] (wherein R ₁ and R′ ₁ are residues provided by the epoxy/imidazole addition reaction, R ₂ and R ₃
and R ₄ are hydrogen atoms or substituents such as preferably alkyl or aryl groups having less than 10 carbon atoms. For example, the formula () or the adduct of the formula () is the formula or expression (In the formula, R _A and R′ _A are a C _1-10 alkyl group or preferably a phenyl group that may be substituted.) The tautomeric nature of imidazoles with unsubstituted imine nitrogen atoms makes it easy for epoxy adducts formed from such imidazoles to be formed as a mixture of two isomeric forms. for example,
In formulas () and (), when one of the groups R ₄ and R ₅ is a hydrogen atom and the other is a substituent, the adduct is likely to be formed in the form of two isomers. That is, one has a substituent at the 4-position of imidazole, and the other has a substituent at the 5-position of imidazole. Preferably, the molar ratio of epoxy to imidazole used to form the adduct does not exceed 2:1, ie only one monofunctional epoxy group is attached to each nitrogen atom, and no polyepoxide, for example, is attached. Higher molar ratios dilute the effectiveness of the curing agent and actually reduce the effectiveness of the complex. Essentially any metal salt can be used in the complex of the metal salt and the imidazole/epoxy adduct. Examples of metal salts are as follows. Copper salts such as cupric chloride, cuprous chloride, cupric bromide, cupric fluoride, cupric nitrate, cupric fluoroborate, cupric sulfate, cupric acetate, trifluoro Cupric acetate, cupric methacrylate, cupric stearate, cupric octonate, cupric malonate, cupric benzoate: nickel salts such as nickel chloride, nickel fluoride, nickel sulfate, fluoride Nickel borate, nickel tholeate, nickel stearate and nickel castor oil salts: Calcium salts such as calcium chloride and calcium bromide; Cobalt salts such as cobaltous chloride, cobaltous fluoride, cobaltous sulfate, stearate Monocobalt, cobaltous octonate and cobaltous borate fluoride: Zinc salts such as zinc bromide, zinc stearate, zinc octonate, zinc 2-ethylhexonate, zinc chromate and zinc chloride: Mercury salts such as bromide Mercury and mercuric chloride: Zirconium salts such as zirconium sulphate: Indium salts such as indium fluoroborate: Silver salts such as silver nitrate: Chromic acids such as chromic chloride: Manganese salts such as manganese chloride and manganese sulphate: Tin salts such as chloride Stannous: cadmium salts such as cadmium chloride: iron salts such as ferrous chloride: titanium salts such as titanium chloride. Preferred metal salts are CuCl ₂ , CuBr ₂ , Cu(NO ₃ ) ₂ ,
Copper acetate, copper propionate, CaCl ₂ , CoCl ₂ , ZnCl ₂
and cadmium acetate. The above metal salts are only a partial list of the metal salts that can be used. The molar ratio of metal salt to imidazole/epoxy adduct is not critical. However, generally the molar ratio of metal salt to imidazole epoxy adduct is from 1:1 to 1:6, preferably 1:4. Complexes of imidazole epoxy adducts and metal salts are conveniently produced by mixing the components. If any of the above components are solids, solutions of the reactants in a solvent such as methanol or water can be used. If the product is a solid, the resulting precipitate can be filtered to obtain the complex. A composition that is one aspect of the present invention is an epoxy resin or monoepoxide containing the imidazole metal salt complex as a curing agent. The composition includes:
The imidazole/epoxy complex and the epoxy resin or monoepoxide can be formed by simply mixing with or without a solvent. Each component can be mixed at room temperature. Any epoxy resin or monoepoxide can be cured by mixing the epoxy resin or monoepoxide with the imidazole/epoxy metal salt complex and heating the mixture to about 200-500°C. The epoxy resin or monoepoxide can be saturated or unsaturated, or cycloaliphatic, heterocyclic or aliphatic;
Furthermore, if desired, substituents such as halogen atoms, sulfur atoms, ester residues, urethane residues, amino groups, hydroxyl groups, ether groups, mercapto groups, acid groups,
It may also be substituted with anhydride, ketone and aldehyde residues. The epoxy resins or monoepoxides mentioned can be monomeric or polymeric. Furthermore, halogen atoms, sulfur atoms, hydroxyl groups, mercapto groups,
It can be used in the presence of compounds or resins containing ether residues, amino groups, acid groups, anhydride residues, ester residues, urethane residues, ketone residues and aldehyde residues. In this specification, "epoxy resin" means polyepoxide. The monoepoxide polymerizes when mixed with the imidazole/epoxy metal salt complex and heated. Therefore, in the case of monoepoxides, the curing agent referred to herein means a polymerizing agent. Monoepoxides which polymerize when the imidazole/epoxy metal salt complex is added and heated are, for example, propylene oxide, allyl glycidyl ether, phenyl glycidyl ether, pentachlorophenyl glycidyl ether, tetrabromphenyl glycidyl ether and glycidyl methacrylate. In a preferred embodiment, the epoxy resin is a polyepoxide having an average of more than 1.0 1,2-epoxy groups per average molecular weight. Among the polyepoxides that can be used in the present invention, polyglycidyl ethers of polyphenols such as Bisphenol-A are preferred. These can be obtained, for example, by etherifying polyphenols with epichlorohydrin or dichlorohydrin in the presence of an alkali. Examples of phenolic compounds include 2,2-bis(4-hydroxyphenyl)propane, 4,4'-dihydroxybenzophenone, 1,1-bis(4-hydroxyphenyl)ethane, and 2,2-bis(4-hydroxyphenyl)ethane. -Hydroxy-t-butylphenyl)propane, bis(2
-hydroxynaphthyl)methane or 1,5-dihydroxynaphthalene. The polyphenol can also be a novolac resin. Polyepoxides of this type are, for example, the reaction products of bisphenol-A and epichlorohydrin. Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 2,
Similar polyglycidyl ethers of polyhydric alcohols which can be derived from 4,6-hexanetriol, glycerin and trimethylolpropane are also suitable. Other examples of polyepoxides that can be used in the present invention are partial fatty acid esters of the aforementioned glycidyl polyethers of polyhydric alcohols and glycidyl polyethers of polyhydric phenols. Fatty acids that can be used to produce these resins are, for example, linseed oil and castor oil. Epichlorohydrin or similar epoxy compounds and aliphatic or aromatic polycarboxylic acids such as oxalic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,5-naphthalenedicarboxylic acid and 2
Polyglycidyl esters of polycarboxylic acids produced by reaction with merized linolenic acids are also suitable. Other examples are polyepoxides derived from the epoxidation of olefinically unsaturated aliphatic compounds. Included are diepoxides and higher epoxides, as well as epoxide mixtures consisting in part of one or more monoepoxides. These polyepoxides are nonphenolic and are obtained by epoxidizing olefins such as butadiene and cyclohexene, for example with oxygen and selected metal catalysts, with perbenzoic acid, with acetaldehyde monoperacetate, or with peracetic acid. The ratio of imidazole/epoxy adduct metal salt complex to epoxy resin is not critical.
Generally, the mixture will contain from about 0.5 to about 4.0 parts by weight of metal salt complex per 100 parts by weight of epoxy resin. When the epoxy resin or monoepoxide and the imidazole metal salt complex are mixed together, the composition can be stored at room temperature for extended periods without curing or polymerization. If the epoxy resin is used as a sheet material, it can be heated for as long as necessary to form a hard gelling material. When the epoxy mixture is used as a coating or adhesive, the mixture is coated onto a substrate and heated for a sufficient period of time to cure the resin and form a hard adhesive coating on the substrate. The amount of heat required to cure the epoxy mixture will vary depending on the particular components, but generally the mixture will be heated to about 90 to about 250 degrees Celsius until the resin is cured. If rapid curing and improved high temperature strength are desired, an epoxy resin or monoepoxide can be mixed with the mixture of the metal salt complex and nitrogen compound. This composition can be produced by simply mixing the complex and nitrogen compound with the epoxy resin or monoepoxide. The ratio of curing agent to epoxy resin or monoepoxide is the same as without added nitrogen compound. The curing agent can contain the imidazole complex in any proportion to the nitrogen compound. However, the best results are obtained when using curing agents containing 1 to 98% by weight of nitrogen compounds. Nitrogen compounds are, for example, aromatic polyamides such as bis(4-aminophenol)sulfone. Metal salt imidazole/epoxy adducts can therefore be used as solubility promoters together with other hardeners, such as the nitrogen compounds mentioned above. Pigments such as titanium dioxide, carbon black, fillers and flexibilizing agents can be added to the epoxy resin composition. Other resinous materials co-reactive with the epoxy resin may be present in the compositions of the invention, such as carboxyl groups such as axelaic acid.
resins containing anhydrides such as Nadic (trade name) anhydrides, polyesters containing epoxy groups, resins containing hydroxyl groups, resins containing thio groups, silicone resins containing epoxy groups,
Urethane resins and resins containing amino groups can also be included. Addition of the co-reactants described above can be carried out to impart a variety of known desired properties to the epoxy resin composition. The metal salt imidazole/epoxy adduct complexes used in the compositions of the present invention are curing agents that generally have better solubility in epoxy resins than known metal salt imidazole complexes. The complexes according to the invention are relatively soluble in organic solvents and are generally non-reactive with epoxy resins at room temperature, but in one-component epoxy systems (one-component compositions) at elevated temperatures, e.g., above about 100°C. Effective as a hardening agent.
As already evident, the compositions can be stored for long periods of time without premature curing and without formation of agglomerates and caking of the curing agent. Second, the present invention relates to imidazoles and carbon atoms 20
A one-component epoxy composition, which is a complex of an adduct with up to 1,000 monofunctional epoxy compounds and a metal salt, and which can be cured or polymerized by heating with an epoxy resin, a monoepoxide, or a mixture of an epoxy resin and a monoepoxide. Provide complexes suitable for forming products. The metal salt complex can be any of the novel metal salt imidazole/epoxy complexes described above. The present invention will be explained in more detail below using examples. Example 1 Preparation of a 1:1 molar adduct of imidazole (Im) and phenyl glycidyl ether (PGE) To a stirred refluxing solution of 17 g (0.25 mol) of imidazole in 200 cm ³ of benzene is added in 50 cm ³ of benzene over the course of 1 hour. 37.5g of phenyl glycidyl ether
Add a solution of (0.25 mol). The reaction mixture is kept under reflux for a further hour, and then the solvent is removed by rotary evaporator. A pale yellow, slightly opaque viscous product is obtained with a yield of 52.5 g. Example 2 Preparation of 1:1 molar adduct of 2-ethyl-4(5)-methylimidazole (EMI) and PGE Stirred reflux of 27.5 g (0.25 mol) of 2-ethyl-4-methylimidazole in 200 cm ³ of toluene A solution of 37.5 g (0.25 mol) of phenyl glycidyl ether in 50 cm ³ of toluene is added to the solution over the course of 1 hour. The reaction solution is kept under reflux for a further 2 hours and then allowed to cool. The product is precipitated, washed with p.eth. 40-60 and dried in a vacuum oven at 40°C. An orange viscous product is obtained with a yield of 45.6 g. Example 3 Preparation of ^a 1:2 molar adduct with EMI and PGE A stirred refluxing solution of 11 g (0.1 mol) of 2-ethyl-4-methylimidazole in 100 cm 3 of toluene was added in 50 cm ³ of toluene for 2 hours. A solution of 30 g (0.2 mol) of enyl glycidyl ether is added.
The reaction mixture is kept under reflux for an additional hour and then allowed to cool. A brown viscous product precipitates,
Wash with p.eth. 40-60 and dry at 40°C in a vacuum oven. Yield is 33.5g. Example 4 Preparation of a _complex of 1:1 molar adduct of PGE and In with CuCl ₂ [Cu(PGE・Im) ₄ Cl ₂ ] 15.7 g of adduct PGE・Im in 50 cm ³ of methanol
(0.072 mol) of methanol while stirring.
A solution of 3.05 g (0.01794 mol) of CuCl ₂ .2H ₂ O in 25 cm ³ is added. Initially a light blue precipitate forms which is dissolved by further addition of CuCl ₂ /methanol solution to give a dark blue solution.
The solution is reduced in volume at 40° C. in a vacuum oven and finally dried. A dark blue, crumbly product is obtained. Example 5 Preparation of a complex of 1:1 molar adduct of PGE and EMI with CuCl ₂ [Cu(PGE・EMI) ₄ Cl ₂ ] 10.00 g of adduct PGE・EMI in 50 cm ³ of methanol
(0.0385 mol) of CuCl _{2.2H 2} O in 20 cm ³ of methanol while stirring into a solution of 1.6346 _g (0.0096 mol)
Add the solution. After slow evaporation of the solvent over 16 hours, a dark green residue is obtained. Drying in a vacuum oven at 40°C yields 9.4 g of a dark blue, brittle, resinous product. Example 6 Preparation of a complex of 2:1 molar adduct of PGE and EMI with CuCl ₂ [Cu(PGE ₂ .EMI) ₄ Cl ₂ ] 9.69 g of adduct PGE ₂ EMI in 40 cm ³ of methanol
(0.0236 mol) is added with stirring a solution of 1.0044 g (0.0059 mol) of CuCl ₂ .2H ₂ O in 10 cm ³ of methanol. The resulting dark green solution is evaporated to a green resinous material, which is finally dried at 40° C. in a vacuum oven. The product is a dark green, highly viscous resinous material. Example 7 Preparation of a 2:1 molar adduct of PGE and EMI The adduct PGE _2. dissolved in 5 cm ³ of methanol.
To a solution of approximately 2 g of a precisely weighed sample of EMI is added, with stirring, a solution of a precisely weighed sample of the stoichiometrically required metal salt in approximately 10 cm ² of methanol. Evaporate the solvent at room temperature and leave the last traces in vacuo
Remove at 50°C. A summary of the compositions of the various complexes is given in Table 1 below. Example 8 Experimental evaluation of the activity of the complex as a curing agent for the epoxy resin Shell E pikote 828 (trade name) Epikote 828 is an example of a group of polyepoxides produced by the reaction of bisphenol-A with epichlorohydrin. The complexes prepared in Examples 6 and 7 above are incorporated into a resin sample to provide a composition containing about 5 parts by weight (pph) of complex per 100 parts by weight of resin. Add a precisely weighed epoxy resin sample to approximately 0.05 g of a precisely weighed complex sample, and add approximately 5 cm ³ of acetone.
to make the complex concentration 5.0 pph. The mixture is stirred, with gentle warming if necessary, until the complex is dissolved. The acetone is then removed in a vacuum oven at 50°C. A 10-30 mg sample of the mixture in an aluminum pan was heated using a differential scanning calorimeter (DSC) at a heating rate of 10 K/min.
Scan in Dupont910. The output from the instrument is plotted as heatflow versus temperature. Curing of the resin is characterized by an exotherm that appears as a peak or a rapid peak in the output. The onset of exotherm on the initial baseline is used as a standard for measuring the onset of cure, and any sequential peaks in the heat flow output are considered characteristic of the cure reaction. Results with various complexes are included in Table 1 below. Example 9 Curing of epoxy resin MY720 (Ciba-Geigy)
This is an example of polyglycidylamine. Most of MY720 is tetra-N-glycidyl-bis(4
-aminophenyl)methane. 0.054 g of a complex with the composition Cu(PGE・EMI) ₄ Cl ₂ was added to 0.982 g of the resin sample, and heated to 100°C.
Obtain a solution by stirring for a few minutes. The sample is scanned in the DSC with a heating rate of 10 K/min. A large amount of heat of curing is observed at an onset of 102°C. The second sample is cured in an aluminum pan in an oven at 200°C for 2 hours. Next, when this was scanned in DSC at 20K/min, an endothermic change, which is characteristic of the glass transition point, was observed at 208°C, indicating a high degree of hardening. Example 10 MY720 is often cured with aromatic polyamines, and bis(4-aminophenyl) sulfone (BAPS) is often used specifically for this purpose. Due to the low reactivity of BAPS, promoters such as a complex of boron trifluoride and ethylamine are commonly added. 2459g of MY720 resin and 0.738g of BAPS at 135℃
Mix for 15 minutes to form a solution. Add composition Cu (PGE/
EMI) Add 0.114 g of a complex with ₄ Cl ₂ to form a solution. Weigh 28.2g of the sample, put it in an aluminum pan, and heat it at a heating rate of 10K/min in the range of 40℃ to 290℃.
Scan in DSC. The onset of the curing exotherm is observed at about 110°C, and the exothermic peak temperature is about 200°C. The second scan of the sample at a heating rate of 20 K/min is
It showed a glass transition temperature of 189°C, proving that a high degree of hardening was achieved. Similar experiments without the complex show an onset of curing at about 160°C and an exothermic peak at about 260°C. This indicates that the complex is an effective promoter of the curing reaction.

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Claims (1)

[Claims] 1. A metal salt complex of an adduct of an imidazole and a monofunctional epoxy compound, and (b) an epoxy resin, a monoepoxide, or a mixture of an epoxy resin and a monoepoxide, by heating. A one-component epoxy composition that can be cured or polymerized. 2 The adduct is imidazole or 2-ethyl-
The composition according to item 1 above, which is produced from 4-methylimidazole. 3. The composition according to item 1, wherein the adduct is produced from an epoxy compound having up to 20 carbon atoms. 4. The composition according to item 3 above, wherein the epoxy compound is glycidyl ether. 5. The composition according to item 4 above, wherein the epoxy compound is phenyl glycidyl ether. 6. The composition according to item 1, wherein the molar ratio of the imidazole to the epoxy used to form the adduct is from 1:1 to 1:2. 7 The metal salts used for complex formation are CuCl ₂ ,
CuBr ₂ , Cu(NO ₃ ) ₂ , copper acetate, copper propionate,
2. The composition according to item 1, which is selected from the group consisting of CaCl ₂ , CoCl ₂ , ZnCl ₂ and cadmium acetate. 8. The composition according to item 1, wherein the molar ratio of the metal salt to the adduct used for complex formation is 1:1 to 1:6. 9. The composition according to item 1, further comprising at least one nitrogen compound in addition to the complex. 10. The composition according to item 9, further comprising at least one aromatic polyamine as the nitrogen compound. 11 The ratio of complex to epoxy resin or monoepoxide is 0.5 to 40 parts by weight of complex to 100 parts by weight of epoxy resin or monoepoxide,
The composition according to item 1 above.